The side chain signal in the lower half of the diagram is derived from either the main stereo input (1 & 2) or an external stereo input (3 & 4) as determined by the 'External' switch. It can then be adjusted using the 'Trim' and 'Low Cut' controls before being used to determine the gain reduction applied to the main signal flow, shown in the upper part of the diagram.

The 'Listen' switch can be used to temporarily divert the sidechain signal to the audio output to allow the signal to be monitored, both aurally and via the input level meter.

The 'Mix' control combines the uncompressed signal (after the input trim control) with the compressed signal (after the makeup gain control) to provide for so-called 'New-York' or parallel compression techniques, or to simply compare the compressed output signal with the original uncompressed input.